Chelsea goalkeeper Petr Cech confident ahead of cup clash

United, the runaway Barclays Premier League leaders and 19 points clear of fourth-placed Chelsea, last won the FA Cup in 2004. Since 2007 the Blues have dominated the competition, with four wins in six years.

"They are the favourites for the game, but it's the FA Cup and in the FA Cup not every time do the favourites win," Cech told Chelsea TV. "We're still the holders, so we'll try to keep our trophy as long as we can."

The rivals warmed up for the Old Trafford clash with European defeats, but, while United lost to Real Madrid in the Champions League, Chelsea suffered a humiliating 1-0 loss at Steaua Bucharest in the Europa League.

Following the highs of Wembley and Munich last May, Chelsea are enduring a torrid 2012/13 season and became the first holders to exit the group stage of the Champions League last November. The FA Cup has not been plain-sailing, either.

The Blues needed a replay to defeat npower League One Brentford, then claimed a 2-0 win at Middlesbrough in a fifth round tie overshadowed by comments made by interim manager Rafael Benitez.

The Spaniard hit back at his continual barracking by the club's supporters, telling them to use their energies to support the team as he is to leave at the end of his short-term contract in May and criticising the decision to name him 'interim manager', rather than just 'manager'.

Benitez will renew hostilities with United boss Sir Alex Ferguson, with whom he had a frosty relationship while at Liverpool, at Old Trafford, where the hosts will be looking to prove a point following their Champions League elimination to Jose Mourinho's Madrid in midweek.

Chelsea defender Branislav Ivanovic said: "It is going to be one of our biggest challenges of the season, especially playing them at this moment.

"When you go out of the biggest competition in that way, it must be disappointing but they will be more motivated because of that."